Apparatus for quenching web material



Dec. 19, 1967 H. 1.. TAYLOR 3,358,980

APPARATUS FOR QUENCHING WEB MATERIAL Original Filed Nov. 21, 1961 2 Sheets-Sheet 1 FROM 575,4 u SUPPI Y I-- COA/TPOllIE L w j g aa .30 f 16 Ouewuv L WA T62 T 7 Hr-,7 SU/Pl y 17 i: I 4Z0 1: 9

IN V EN TOR.

Dec. 19, 1967 H. L. TAYLOR 3,358,980

APPARATUS FOR QUENCHING WEB MATERIAL Original Filed Nov. 21, 1961 2 Sheets-Sheet 2 Pee ozose (0404 0115? 35 Q Q 29d P6602052 P5609052 X comeozu'e F ro/vreousk Z Of gz wsgoa ,V M a 07/ United States Patent APPARATU FOR QUENCHING WEB MATERIAL Harold L. Taylor, Hammond, Ind., assignor to Inland Steel Company, Chicago, 111., a corporation of Delaware Continuation of application Ser. No. 153,834, Nov. 21, 1961. This application Jan. 21, 1965, Ser. No. 426,988

30 Claims. (Cl. 266-3) ABSTRACT OF THE DISCLOSURE Quench a heated web of material (e.g., tin plate) in a liquid bath. Introduce additional liquid quenching medium to bath at location where web enters bath. Prevent surface turbulence in bath at region where web initially contacts quenching medium. Control temperature and flow rate of additional quenching medium, the same on both sides of web, or different on eachside of web. Control level of bath. Gives product without quench patterns on surface.

This application is a continuation of application Serial No. 153,834, now abandoned, filed by the present inventor on Nov. 21, 1961, and bearing a title corresponding to that of this application.

This invention relates to a method and apparatus for quenching a web of material. In particular, it relates to a method and apparatus for progressively and continuously quenching a moving web of material, such as tin plate, at a selected temperature level.

The invention finds particular application in situations in which the temperature level of the quenching medium is important to the physical or chemical properties of the quenched material. In this aspect, the quenching of tin plate is one important form and, for illustrative purposes, the invention will be explained in this form.

In a conventional electroplating line for tin plate, the coating which results from electroplating has a dull, mat character. In order to brighten the coating of the electroplated material, it is conventional to heat the material until the coating is momentarily melted or in a molten or substantially plastic state, whereupon it is immediately directed into a cooling bath, thereby to be quenched and solidified. It has been found that two distinct types of quench patterns or surface imperfections may result for conditions where the quenching bath temperature is not at the correct level. One type of pattern appears as a light gray stain with very distinct border regions whenever the temperature of the quenching medium is too hot for the desired purpose. This same type of pattern can also occur when the liquid of the quenching bath is splashed or spattered upon the molten coating of the web prior to the full web immersion. The other type of pattern or stain is a dull, dark gray pattern with indistinct boundaries. This is produced whenever quenching occurs within a medium which is too cold for the intended purpose. Both types of patterns appear to the eye as a material deposit upon the electroplated surface. There is, however, not sufiicient material present in these patterns to permit a reliable chemical analysis. Microscopic examination indicates that these patterns are actually a disturbance of the tin itself rather than a deposit of foreign substances.

The method and apparatus of the invention are employed to obviate the aforesaid types of quench patterns and leave a bright, shiny surface. The web surface is cooled almost instantly and in the complete absence of any coolant splash on the web surface. In practicing the method and in employing the apparatus of the invention, a moving web of material, such as steel which has been electroplated with a suitable material, such as tin coating in a molten state, is progressively moved through a quenching bath. Since the thennal gradient between the Patented Dec. 19, 1967 web ofmaterial (immediately before quenching) and the quenching liquid is the greatest in the region where the web of material first contacts the quenching medium, a quenching medium at a selected temperature level is there passed into contact with the web of material. This is'in contradistinction to prior art installations wherein only the mean temperature level of the quenching bath was controlled.

The invention has its basis in the type of control which is achieved in a quenching bath through which the web of material is progressively moved. It has been found that, if the temperature level of the quenching medium is allowed to vary more than about :10 degrees from a suitable optimum value, the above-mentioned quench patterns frequently result. The apparatus of the invention therefore includes means for varying the temperature level or heat removal properties of the quenching medium at the precise region where a moving web of material first contacts the bath of liquid quenching medium. The selected temperature level is dependent upon various conditions, such as the speed of the web of material, the general freedom from turbulence at the place where the web of material moves into contact with the liquid quenching medium, and the amount of heat energy contained by the moving web of material. Once the desired temperature level for the particular set of conditions is determined, the control system of the invention is automatically adjusted to supply a quenching medium at that temperature.

In a specific embodiment of the apparatus of the invention, the web of material with its molten coating on the surface is moved rapidly into and then through a quenching bath contained in a quenching tank. A temperature sensing device is located near the place where the web of material enters the quenching bath, thereby to be sensitive to the temperature level at that place. Usually, a moving web in tin-plate production moves at speeds up to about 1800 feet per minute, with speeds of 800 to 1000 feet per minute being most common. In response to a signal from the temperature sensing device, a controller controls the temperature level of the quenching medium which is passed into contact with the moving web of material at the place where the web of material passes into the quenching bath. When, for example, the temperature level of the quenching medium is too high at the point of entrance of the web, the controller is caused to operate to reduce the temperature level or to increase the rate at which the quenching medium flows into the quenching tank, or both controls may be used to restore the optimum temperature of operation, which is frequently known as the set point temperature.

On the other hand, when the controller receives a signal which indicates that the temperature level of the quenching medium is too low, the controller is caused to operate to raise the temperature level or to decrease the rate at which the quenching medium flows into the quenching tank, or, again, both types of control may be used concurrently if appropriately controlled.

At the quenching tank, the quenching medium is passed into contact with the web of material in such a manner that there is a minimum of turbulence or splashing at the surface of the quenching medium through which the web of material moves. In one form, a quenching hood through which the quenching medium passes has a pair of spaced plates between which the web of material (with the coating thereon in a molten state) moves, although it is emphasized that the various details of construction of the quenching hood are not necessary in order to accomplish the purposes of the invention. After the quenching medium has passed over the upper edges of the spaced plates and then between them, it flows downwardly due to gravity and the surface tension of the moving web of material.

The cooling or quenching liquid medium which flows into the quenching hood compartments passes over baffies and partition elements and finally overflows the upper edges or li s of the spaced plates, thereafter to flow between a pair of closely spaced plates into an enlarged quench tank. The exit flow of the liquid from the large quench tank is finally drawn off at a selected level by permitting it to overflow an adjustable gate.

The inflowing quenching or cooling medium first reaches the web after it overflows the outer edges of the spaced plates of the quenching hood. As the cooling liquid then flows into the quench tank proper, it flows in a path which is between the web and the overfiowed plate and system is employed for each side of the web of material. A liquid quenching medium at a selected temperature level is passed into contact with each of the sides of the moving web of material. The liquid quenching medium is maintained at one selected temperature level when passed substantially parallel to the direction in which the fastenters the bath. The end result is substantially to preclude all possibility that splash marks will appear on the web as a whole. Any splashing of the cooling medium upon the tin plate in its molten or plastic state is sufficient to produce such spotting as substantially to detract from the sales value of the end product.

Even though the surface of the cooling medium is calm and substantially free from turbulence, the movement of i the web beneath the surface of the cooling medium induces considerable turbulence beneath the surface of the quenching bath. This results because of the relatively narrow spacing of the plates and the relatively great speed of the web of material with respect to the quenching medium.

In addition, some turbulence results beneath the surface of the coolant because of the substantial temperature difference between the coolant and the web proper. The

. web, with its coating of tin in a molten or plastic state, enters the cooling bath at a surface temperature in a. range of about 440 F. to about 470 F. The coolant should be maintained somewhere in the range of about 80 F. to about 190 F. Usually at a relatively fast line speed, the bath temperature is lower than when the line speed is relatively slow. The temperature best suited is also determined by the coating thickness and the sheet thickness. Because of the temperature variance between the web and the coolant, the coolant adjacent to the web, at the time when there is the greatest temperature difference between them, may boil and this produces undersurface turbulence which brings fresh coolant in contact with and against the web surface. The result is that, as the web moves through the liquid cooling medium, the liquid is drawn downwardly in the direction of web movement because of surface tension between the liquid and the web, and the liquid coolant circulates relative to the web because of the temperature difference between the coolant and the web. This places a maximum amount of cooling liquid into contact with the web and, as can be appreciated, the turbulence beneath the surface of the quenching bath is highly desirable since the uniformity and completeness of quenching in minimum time is thereby augmented. The liquid level of the quenching bath with respect to the upper portion of the plate is also controllable, so that for a given web speed, given spacing of the plates, given density of the liquid quenching medium, and so forth, the liquid level of the quenching bath can beadjusted to obtain an optimum condition of Ininimum turbulence at the surface of the quenching bath.

When it is desired to coat a differentially coated web of material, that is, a web which is coated on one side with a certain thickness of material and on the other side with a greater thickness of material, a separate control into contact with the one coated side of the web of material, while the quenching medium is at a lower temperature level when passed into contact with the other more thickly coated side of the web of material. Hence it is apparent that a great degree of temperature control is achieved. Here also, the temperature is determined by the web speed, its thickness and the thickness of the tinplate coating applied.

In practicing the method of the invention the liquid quenching medium is caused to flow in the channel formed between the spaced plate and the web and to flow in the direction of web movement. The cooling medium is passed at the selected temperature level into contact with the moving web of material at the place where the web enters the quenching bath and in such a way that turbulence is there avoided.

When a differentially coated Web of material is to be quenched, for optimum results a liquid quenching medium at a different temperature level is passed into contact with each side of the web of material.

Having generally described the invention, reference is now made to the accompanying drawings in which:

FIGURE 1 is a diagrammatic view mainly in cross-section showing in particular the apparatus employed in passing the quenching medium into contact with the moving web of material;

FIGURE 2 is a diagrammatic view showing one system by which the temperature level of the liquid quenching medium is controlled;

FIGURE. 3 is a diagrammatic view showing another system by which the temperature level of the liquid quenching medium is controlled;

FIGURE 4 is a diagrammatic view showing a system particularly adapted for the quenching of a differentially coated web of material employing essentially a duplication of the system shown in FIGURE 2 of the drawings to control the liquid quenching medium which is passed into contact with each side of the web of material; and

FIGURE 5 is a diagrammatic view showing a system particularly adapted for the quenching of a differentially coated web material employing essentially a duplication of the system shown in FIGURE 3 of the drawings to control the liquid quenching medium which is passed into contact with each side of the web of material.

Referring now to FIGURE 1 of the diagrammatic drawings, there is shown a quenching tank 9 which contains a quenching bath 10 through which a web of material 11 moves in the direction shown by the arrows. The term quenching bath is intended to include the quenching medium which has been introduced at the place generally indicated at 12 where the moving web of material contacts the newly introduced liquid quenching medium, which is usually water at controlled temperature. A quenching hood, generally indicated at 13, is employed for passing the liquid quenching medium into contact with the web of material 11. The quenching hood 13 is shown to be divided generally into two compartments 14 and 15, each of which introduces the quenching medium into contact with one side of the web of material. The compartments 14 and 15 have conduits 16 and 17 which lead therein to supply a quenching bath which flows in toward bafile plates 18 and 19 respectively, whch assure thorough mixing of the liquid quenching medium. The compartments 14 and 15 contain sumps 20 and 21 which assure that there is not a great deal of turbulence in the liquid quenching medium when it passes over a pair or lips 22 and 23 of a pair of spaced plates 24 and 25 between which the web with its molten tin coating is passed. The

liquid quenching medium which passes over the lips 22 and 23 reaches the region where the flow into the tank 9 is along a path substantially parallel to web travel and the liquid quenching medium is most effective in quenching of the incoming web at the region indicated at 12.

A temperature sensing device, indicated generally at 26, comprises a pair of temperature sensing elements 27 and 28 to determine the temperature level of the liquid quenching medium at about the region where the web and strip are first in contact. This element is any well known type of unit for temperature sensing and from which it is customary to develop an electrical signal to actuate or control a controller 29 over a line 30 (see FIG. 2, for instance). The controller 29 is preferably a recorder controller, that is, one which not only has a function of controlling some other component but also of recording the temperature level sensed by the temperature sensing device 26.

While various forms of temperature sensing and control elements may be used, the operation has been carried out with a pressure regulator and filter of the Brown Instrument Corp. type, such as the #358249-1, and an air-operated indicating and recording electronic potentiometer of the same company, Model #152P13, PSHl- 96-Kl1l-A1A4, operated in conjunction with a Minneapolis-Honeywell thermocouple having a pressure tight protecting well with a sensitive tip for securing purposes, such as its Sensitive Tip Model M.S. 9M9A-2, an element Model 9J30ADY2-2A and a general purpose head Model 9M1B.

As shown in the control system of FIGURE 2 of the drawings, a conduit 31 leads from a source of steam supply into a conduit 32 which leads from a source of liquid quenching medium supply. The conduit 31 contains a manually operable valve 33 of any suitable form which is employed for varying the flow rate of the inlet steam. The conduit 32 has disposed therealong a modulating or flow-control valve 34 which is operated from a signal over a line 35 which leads from the controller 29. When the temperature sensing device 26 sends a signal to the controller 29, for example, to indicate that the temperature level of the liquid quenching medium is too low, the controller 29 operates to modulate the valve 34 to permit less liquid quenching medium to flow through the conduit 32. When, on the other hand, the temperature sensing device 26 indicates to the controller 29 that the temperature level of the liquid quenching medium is too high, the controller modulates the valve 34 to permit a greater quantity of liquid quenching medium to pass through the conduit 32, into conduits 16, 17.

The diaphragm control valve 34 may be a Minneapolis- Honeywell unit control valve with a Moore positioner Series 800l1 usually operating in air-to-close fashion.

An overflow device generally indicated at 40 is employed as an outlet for the quenching bath which is constantly being increased by the supply of liquid quenching medium. The device 40 is preferably made adjustable in character so that the liquid level above the lips 22 and 23 of the plates 24 and 25 can be varied so that the minimum of turbulence is experienced where the moving web contacts the place of contact 12 of the liquid quenching bath. The device 40 includes an adjustable gate 41 which is pivoted about a hinge 42. An adjusting screw 43 is adapted to be turned by a handwheel 44 to pivot the gate 41 about the hinge 42. The adjusting screw 43 passes through an internally threaded ball 45 which is supported in a socket 46 which is attached, for example, to the tank 9.

Referring now to FIGURE 3 of the diagrammatic drawings, a modified arrangement is shown for controlling the temperature level of the liquid quenching medium. A conduit 31a leads from a suitable source of steam supply into a conduit 32a which leads from a suitable source of liquid quenching medium supply. The conduit 31a has disposed therealong a valve 33a which is operated under the influence of the recorder controller, while the conduit 32a has disposed therealong a manually operable valve 34a. In the control system shown in FIGURE 3, the recorder controller 29a controls the steam inlet through the valve 33a by a signal through a line 35a. The flow through the valve 34a to provide quenching liquid is manually operated. The main difference between the system shown in FIGURE 2 and FIGURE 3 is that in FIGURE 2 the controller 29 controls the quantity of liquid quenching medium which is supplied to the conduits 16 and 17, while in the system of FIGURE 3 the quantity of liquid quenching medium which is supplied to the conduits 16 and 17 is relatively constant, but the temperature level of the liquid quenching medium is varied in response to a signal from the controller 29a.

In the embodiment of FIGURE 4 of the diagrammatic drawings, a duplication of the system shown in FIGURE 2 of the drawings is employed so that when required a liquid quenching medium at a selected temperature level can be passed into contact with each of the sides of a differentially coated moving web of material. One temperature sensing device 260 sends a signal to the recorder controller 29c over a line 302. The signal from the recorder controller 290 is passed to a modulating valve 340 over a line 352 to modulate the valve opening thereof. A conduit 31c leads from a source of steam supply into a conduit 32c which leads from a source of liquid quenching medium supply. The conduit 310 contains a manually operable valve 332. Similarly, a temperature sensing device 26d senses a signal from the other side of the Web of material to a recorder controller 29d over a line 300.. The recorder controller 29d operates a modulating valve 34d with a signal which passes through line 35d. A conduit 31d leads from a source of steam supply into a conduit 32d which leads from a source of liquid quenching medium supply. The conduit 31d contains a manually operated valve 33d. Instead of the conduit 32 leading into branch conduits 16 and 17 as shown in FIGURES 2 and 3 of the drawings, the conduits 32c and 32d lead directly into the respective compartments 15 and 14 of the quenching hood 13.

In the embodiment of FIGURE 5 of the drawings, a temperature sensing device 262 disposed on one side of the web of differentially coated material 11a passes a signal over a line 392 to a recorder controller 292. A conduit 312 leads from a source of steam supply into a conduit 322 which leads from a source of liquid quenching medium supply. A conduit 322 has a manually operated valve 342 disposed therealong, while the conduit 312 has a modulating valve 332 disposed therealong. The recorder controller 292 controls the opening of the valve 332 through a signal which passes through line 352. A temperature sensing device 26 disposed on the other side of the web of material 11a sends a signal through a line 30 to a recorder controller 29 A conduit 31 which leads from a source of steam supply leads into a conduit 32 which leads from a source of liquid quenching medium supply. A manually operated valve 34 is disposed along the conduit 32f while a modulating valve 33 is disposed along the conduit 31 The valve 33 is controlled by a signal from the recorder controller 29 which passes through a line 35].

The above-described embodiments and method being exemplary only, it will 'be understood that the present invention comprehends organizations and methods differing in form or detail from those presently described. Accordingly, the invention is not to be considered as limited, save as is consonant with the scope of the following claims.

What is claimed is:

1. In an apparatus for continuously quenching a substantially continuously moving web of material fed into and withdrawn from a tank containing a bath of liquid quenching medium: means for initially contacting said moving web with additional liquid quenching medium at the place where the web enters said bath; means for preventing surface turbulence in the liquid quenching medium in the region of initial contact between themedium and the web; and means for controlling the temperature of said additional liquid quenching medium.

2. In the apparatus of claim 1: means for varying the liquid level of said bath.

3. In an apparatus for continuously quenching a substantially continuously moving Web of material fed into and withdrawn from a tank containing a bath of liquid quenching medium: means for initially contacting said moving web with additional liquid quenching medium at the place where the web enters said bath; means for preventing surface turbulence in the liquid quenching medium in the region of initial contact between said medium and the web; means, disposed substantially adjacent the place of initial contact between the web and the qunching medium, for sensing the temperature of the liquid quenching medium; and means, responsive to said sensing means, for controlling the temperature of said additional liquid quenching medium.

4. In an apparatus for continuously quenching a substantially continuously moving web of material fed into and withdrawn from a tank containing a bath of liquid quenching medium; means for initially contacting said moving Web with additional liquid quenching medium at substantially the place where the web enters said bath; means for maintaining said liquid quenching medium substantially free from surface turbulence in the region of initial contact with said web; means, disposed substantially at said place of contact, for sensing the instantaneous temperature of the liquid quenching medium; and means, responsive to said sensing means, for controlling the flow rate of additional liquid quenching medium which passes into quenching contact with said web.

5. In an apparatus for continuously quenching a web of material continuously fed into and withdrawn form a tank containing a bath of liquid quenching medium: means for initially contacting said web with additional liquid quenching medium at the place where the web enters said bath; means for maintaining the liquid quenching medium substantially free of surface turbulence at the region of initial contact with the web; means for introducing steam into said additional liquid quenching medium before the latter is passed into contact with said web; means, disposed substantially at the place of initial contact between the web and the liquid quenching medium, for sensing the temperature of the liquid quenching medium at the region of initial contact with ahe web; and means, responsive to a sigal received from said sensing means, for controlling the amount of steam introduced into said additional liquid quenching medium, to control the temperature thereof.

6. In an apparatus for continuously quenching a differentially coated Web of material substantially continuously entering and leaving a cooling tank containing a bath of liquid medium: means for initially contacting the relatively thinly coated side of said Web with a first additional liquid quenching medium, in a substantially turbulent-free state, at the place where the web enters said bath; first sensing means for coninuously sensing the temperature of the first additional liquid quenching medium at substantially the region of initial contact thereof with the web; means, activated by said first sensing means, for controlling the temperature of the first additional liquid quenching medium; means for independently initially contacting the other, more thickly coated side of said web with a second additional liquid quenching medium, in a substantially turbulent-free state, at the place where the web enters said bath; second sensing means for continuously sensing the temperature of the second additional liquid quenching medium at substantially the region of initial contact thereof with the web; and means activated by said second sensing means for controlling the temperature of the second additional liquid quenching medium.

7. A method for continuously quenching a web of material having thereon a coating of a second material of lower melting point, said second material being in a substantially molten state and at a selected temperature, said method comprising the steps of: moving the web along a selected path for immersion in a bath of liquid quenching medium, thereby to harden and solidify said coating; introducing additional liquid quenching medium into said bath; initially contacting said Web with said additional liquid quenching medium at substantially the location where the web enters the bath; directing said additional liquid quenching medium, from the time it enters the region of initial contact with the web, in a confined flow inwardly into said bath, away from the surface thereof, along a path extending alongside said web and in the same direction as that in which the web moves, so that the surface of the liquid quenching medium is substantially free of turbulence and the web enters the cooling medium substantially in the absence of liquid splash; continuously sensing the temperature of the liquid quenching medium at substantially the region where the web enters the bath; and regulating the flow rate of additional liquid quenching medium introduced into said bath to maintain a selected temperature differential between said second material and said bath at said region of web entry.

8. A method for continuously quenching a web of material differentially coated on each side with a second material in a substantially molten state, said method comprising the steps of: feeding said coated web through a bath of liquid quenching medium; introducing additional liquid quenching medium into said bath; initially contacting said W613 with said additional liquid quenching medium at the location where said web enters said bath, and on each side of the Web; directing said additional liquid quenching medium, from the time it enters the region of initial contact with the Web, inwardly into the bath, away from the surface thereof, along a path eX- tending alongside the Web and in the same direction as that in which the web moves, thereby to provide a turbulencefree liquid surface at the region of initial contact between a web surface and the liquid quenching medium; sensing the temperature of the liquid quenching medium on each side of the web at substantially the re gion of initial contact between the web surface and the liquid quenching medium; and controlling the fiow rate and temperature of the additional liquid quenching medium, on each side of the web, in accordance with said sensmg step.

9. In an apparatus for continuously quenching a substantially continuously moving web of material coated with a second mate-rial in a molten state: means for contaming a bath of liquid quenching medium; means for passing said web through said bath; means for flowing additional liquid quenching medium into said bath; means for initially contacting said Web with said additional liquid quenchmg medium at the place where the Web enters the bath; means for preventing surface turbulence in the liquid quenching medium in the region of initial contact between the web and the liquid quenching medium; and means for controlling at least one of (a) the temperature and (b) the rate of how of the additional liquid quenching medium.

10. In an apparatus for continuously quenching a substantially continuously moving web of material having a molten coating on the surface thereof: tank means for containing a bath of liquid quenching medium; means for feeding said web through said bath; means for introducing additional liquid quenching medium into said bath; means for initially contacting said web with said additional liquid quenching medium at the location where the web enters the bath; means for preventing surface turbulence in the liquid quenching medium in the region f initial contact between the medium and the web; said turbulence-preventing means comprising means for directing said additional liquid quenching medium from the time it enters said region of initial contact, inwardly into said bath, away from the surface thereof, along a path extending alongside said web and in the same direction as that in which the web moves; and means for controlling the temperature of the additional liquid quenching medium.

11. In the apparatus of claim 10: means for varying the liquid level of said bath.

12. In the apparatus of claim 10: means to limit the liquid, in said region of initial contact, substantially to liquid quenching medium the temperature of which is controlled.

13. Apparatus for continuously quenching a substantially continuously moving web of material having thereon a coating in a substantially molten state, said apparatus comprising: tank means for containing a bath of liquid quenching medium; means for passing said moving web through said bath; means for passing a confined flow of additional liquid quenching medium into said bath; means for initially contacting said web with said additional liquid quenching medium at substantially the place where the web initially enters said bath; means for maintaining the region of initial contact between the web and the liquid quenching medium substantially free from surface turbulence; said last-recited means comprising means for directing said additional liquid quenching medium, from the time it enters said region of initial contact, inwardly into said bath, away from the surface thereof, along a path extending alongside said web and in the same direction as that in which the web moves; means for introducing steam into said additional liquid quenching medium before the latter contacts said web; means, disposed substantially at the place of initial contact between the Web and the liquid quenching medium, for sensing the instantaneous temperature of the liquid quenching medium; and means, responsive to said sensing means, for controlling the rate at which additional liquid quenching medium passes into said bath.

14. In an apparatus for continuously quenching a substantially continuously moving web of materials having a second material, in a molten state, coating its opposite sides, with the coating being of different thickness on each side of the web: tank means for containing a bath of liquid quenching medium; means for passing said web through said bath; means for introducing additional liquid quenching medium into said bath; means for initially contacting said web, on each side thereof, with said additional liquid quenching medium at the region where the web enters the bath; means for preventing surface turbulence within the liquid quenching medium at the region of initial contact between the web and the liquid quenching medium; said turbulence-preventing means comprising means for directing the flow of said additional liquid quenching medium, from the time it enters said region of initial contact, inwardly into the bath away from the surface thereof along a path extending in the direction of web movement; means for sensing the instantaneous temperature of the liquid quenching medium in said region of initial contact, and on each side of said web; means for controlling the temperature and the flow rate of the additional liquid quenching medium, independently on each side of said web, in response to said sensing means; means to introduce and restrict turbulence in the liquid quenching medium to a sub-surface region of said bath, along said path; and means for removing liquid quenching medium from said bath so that the circulation of liquid quenching medium occurs between said region of initial contact and the liquid removal point.

15. A method for quenching a web of material in a bath of liquid quenching medium, said method comprising the steps of:

introducing said web into said bath of liquid quenching medium;

introducing additional liquid quenching medium into said bath;

contacting a surface of said web with said additional liquid quenching medium, initially at substantially the location where the web enters the bath; and preventing surface turbulence in said liquid quenching medium in the region of initial contact with said web;

whereby surface imperfections on said material, arising from quenching-bath splash, are avoided.

16. A method as recited in claim 15 wherein said step of preventing surface turbulence comprises moving said additional liquid quenching medium, from the time it enters said region of initial contact, inwardly into said bath away from the surface of the bath along a path extending alongside said web and in a direction substantially the same as that in which the web moves.

17. A method as recited in claim 16 and comprising producing turbulence in said additional liquid quenching medium as it moves along said path, at a location below the surface of the liquid quenching medium.

18. A method as recited in claim 16 and comprising:

controlling the rate of heat removal from the web to the liquid quenching medium at the location of ini tial contact between the web and the liquid quenching medium and inwardly from said location along said path;

whereby surface imperfections on said material, arising from improper heat removal rates are avoided.

19. A method for quenching a web of material in a bath of liquid quenching medium, said method comprising the steps of:

introducing said web into said bath of liquid quenching medium;

introducing additional liquid quenching medium into said bath;

contacting a surface of said web with said additional liquid quenching medium, initially at substantially the location where the web enters the bath;

and moving said additional liquid quenching medium,

from the time it enters the region of initial contact, inwardly into said bath away from the surface of the bath along a path extending alongside said web and in a direction substantially the same as that in which the web moves.

20. A method as recited in claim 19 and comprising:

controlling the rate of heat removal from the web to the liquid quenching medium at the location of initial contact between the web and the liquid quenching medium and inwardly from said location along said path;

whereby surface imperfections on said material, arising from improper heat removal rates, are avoided.

21. A method as recited in claim 20 wherein said step of controlling heat removal comprises controlling the temperature of said additional liquid quenching medium.

22. A method as recited in claim 20 wherein said step of controlling heat removal comprises controlling the rate at which said additional liquid quenching medium is introduced into said bath.

23. Apparatus for quenching a moving web of material in a bath of liquid quenching medium, said apparatus comprising:

means for containing said bath of liquid quenching medium;

means for introducing said web into said bath;

means for introducing additional liquid quenching medium into said bath;

means for contacting a surface of said web with said additional liquid quenching medium, initially at substantially the location where the web enters the bath;

and means for preventing surface turbulence in said liquid quenching medium in the region of initial contact with said web;

whereby surface imperfections on said material, arising 7 from quenching-bath splash, are avoided.

24. Apparatus as recited in claim 23 wherein said means for preventing surface turbulence comprises:

means, cooperable with said moving web, to direct said additional liquid quenching medium, from the time it enters said region of initial contact, inwardly into said bath away from the surface of the bath along a path extending alongside said web and in a direction substantially the same as that in which the web moves.

25. Apparatus as recited in claim 24 and comprising means for producing turbulence in said additional liquid quenching medium as it moves along said path, at a location below the surface of the liquid quenching medium.

26. Apparatus as recited in claim 24 and comprising:

means for controlling the rate of heat removal from the web to the liquid quenching medium at the location of initial contact between the web and the liquid quenching medium and inwardly from said location along said path;

whereby surface imperfections on said material, arising from improper heat removal rates, are avoided.

27. Apparatus for quenching a moving web of material in a bath of liquid quenching medium, said apparatus comprising:

means for containing said bath of liquid quenching medium;

means for introducing said web into said bath;

means for introducing additional liquid quenching medium into said bath;

means for contacting a surface of said web with said additional liquid quenching medium, initially at substantially the location where the web enters the bath; and means cooperable with said moving web to direct said additional liquid quenching medium, from the time it enters the region of initial contact, inwardly into said bath away from the surface of the bath along a path extending alongside said web and in a direction substantially the same as that in which the web moves.

28. Apparatus as recited in claim 27 and comprising:

means for controlling the rate of heat removal from the web to the liquid quenching medium at the location of initial contact between the web and the liquid quenching medium and inwardly from said location along said path;

whereby surface imperfections on said material, arising from improper heat removal rates, are avoided.

29. Apparatus as recited in claim 28 wherein said means for controlling heat removal comprises means for controlling the temperature of said additional liquid quenching medium.

30. Apparatus as recited in claim 28 wherein said means for controlling heat removal comprises means for controlling the rate at which said additional liquid quenching medium is introduced into said bath.

References Cited UNITED STATES PATENTS 484,968 10/1892 Logan et a1 2663 2,079,867 5/1937 Meyers. 2,348,232 5/1944 Trautman 134-122 X 2,420,377 5/ 1947 Jones. 2,424,034 7/1947 Hopper 2663 2,892,744 6/1959 Myers 2663 X 3,027,308 3/ 1962 Zulkoski 204207 X OTHER REFERENCES Scientific American, Precision Quenching, November 1945, pp. 274-276.

WILLIAM J. STEPHENSON, Primary Examiner.

R. S. ANNEAR, Assistant Examiner. 

19. A METHOD FOR QUENCHING A WEB OF MATERIAL IN A BATH OF LIQUID QUENCHING MEDIUM, SAID METHOD COMPRISING THE STEPS OF: INTRODUCING SAID WEB INTO SAID BATH OF LIQUID QUENCHING MEDIUM; INTRODUCING ADDITIONAL LIQUID QUENCHING MEDIUM INTO SAID BATH; CONTACTING A SURFACE OF SAID WEB WITH SAID ADDITIONAL LIQUID QUENCHING MEDIUM, INITIALLY AT SUBSTANTIALLY THE LOCATION WHERE THE WEB ENTERS THE BATH; AND MOVING SAID ADDITIONAL LIQUID QUENCHING MEDIUM, FROM THE TIME IT ENTERS THE REGION OF INITIAL CONTACT, INWARDLY INTO SAID BATH AWAY FROM THE SURFACE OF THE BATH ALONG A PATH EXTENDING ALONGSIDE SAID WEB AND IN A DIRECTION SUBSTANTIALLY THE SAME AS THAT IN WHICH THE WEB MOVES.
 27. APPARATUS FOR QUENCHING A MOVING WEB OF MATERIAL IN A BATH OF LIQUID QUENCHING MEDIUM, SAID APPARATUS COMPRISING: MEANS FOR CONTAINING SAID BATH OF LIQUID QUENCHING MEDIUM; MEANS FOR INTRODUCING SAID WEB INTO SAID BATH; MEANS FOR INTRODUCING ADDITIONAL LIQUID QUENCHING MEDIUM INTO SAID BATH; MEANS FOR CONTACTING A SURFACE OF SAID WEB WITH SAID ADDITIONAL LIQUID QUENCHING MEDIUM, INITIALLY AT SUBSTANTIALLY THE LOCATION WHERE THE WEB ENTERS THE BATH; AND MEANS COOPERABLE WITH SAID MOVING WEB TO DIRECT SAID ADDITIONAL LIQUID QUENCHING MEDIUM, FROM THE TIME IT ENTERS THE REGION OF INITIAL CONTACT, INWARDLY INTO SAID BATH AWAY FROM THE SURFACE OF THE BATH ALONG A PATH EXTENDING ALONGSIDE SAID WEB AND IN A DIRECTION SUBSTANTIALLY THE SAME AS THAT IN WHICH THE WEB MOVES. 